Induction-Based Heat Retentive Server

ABSTRACT

A heat retentive server includes a chamber defined between an upper shell and a lower shell that are connected to one another. An induction-heatable member is positioned in the chamber, and the induction-heatable member may be heated by electromagnetic induction to a first temperature that is greater than the heat deflection temperature of the upper shell. Buffering material is positioned in the chamber between the induction-heatable member and the upper shell, and the buffering material is adapted for providing predetermined conductive heat transfer from the induction-heatable member to the upper shell so that at least a portion of the upper shell is heated to a second temperature that is greater than the heat deflection temperature of the upper shell. The second temperature is less than the first temperature.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/827,707, filed Nov. 30, 2017, which is a continuation of U.S. patentapplication Ser. No. 13/934,509, filed Jul. 3, 2013, now U.S. Pat. No.9,854,942, which is a divisional of U.S. patent application Ser. No.13/280,068, filed Oct. 24, 2011, now abandoned. The entire contents ofeach of the above applications are incorporated by reference.

BACKGROUND

The present invention relates to heat retentive servers and, moreparticularly, to heat retentive servers that are heated by induction.

When food is cooked and then served to remotely located consumers, suchas in hotels, aircraft and institutional settings (e.g., hospitals andnursing homes), there is often a delay between the cooked food beingplaced on a plate or other dish, and the food being provided to theconsumer for consumption. Therefore, the food may become cold by thetime it is provided to the consumer, unless steps are taken to keep thefood warm.

It is known to keep food warm in such circumstances by serving it on afood-carrying dish, such as a plate, that is upon a warm or hot heatretentive server (e.g., serving tray), and some of such servers areconfigured for being heated by electromagnetic induction. The plate andfood may be covered with an insulated, dome-shaped cover having a lowerperiphery that substantially seals against an upper periphery of theheat retentive server. The heat retentive server, plate and cover maycollectively be referred to as a “pellet system.” Such induction-basedheat retentive servers or pellet systems have long been recognized as anexcellent choice for keeping food warm.

When using such a pellet system for providing food at a servingtemperature of 140° F. or higher after one hour, it is conventional fora plate that has been washed to thereafter be preheated to at least 165°F. in a dish heater, and then for the food at a temperature of 165° F.to be placed on the preheated plate prior to placing the plate on theinduction-based heat retentive server. It can be disadvantageous topreheat numerous plates, because doing so requires space and energy.Having to preheat numerous plates may also be a safety hazard, sincefoodservice operators may get burned by touching the plate heaters incertain spots.

Thus, there is a need for induction-based heat retentive servers orpellet systems that overcome one or more of the disadvantages of knownsystems and/or otherwise provide a new balance of properties.

BRIEF SUMMARY

One aspect of this disclosure is the provision of a pellet system thatmay be used to transport and serve food so that the food has a servingtemperature of 140° F. or higher after one hour, without preheating thedish of the pellet system. More specifically and in accordance with oneembodiment, a method is provided for using a heat retentive serverhaving an induction-heatable member enclosed within a body. The methodmay include induction heating the induction-heatable member to atemperature greater than the heat deflection temperature of the bodywhile the induction-heatable member is enclosed within the body, placinga dish that is at about room temperature on the body while theinduction-heatable member is enclosed in the body, and allowing heattransfer from the server to the dish to increase the temperature of thedish. The heat transfer from the server to the dish may be buffered bybuffering material positioned between the induction-heatable member andthe body. The food may be placed on the dish prior to placing the dishupon the body of the server. The method may further include washing thedish prior to the placing of the food on the dish, and not heating thedish (e.g., bypassing any dish heater) between the washing of the dishand the placing of the dish on the body of the server. The food and dishmay be covered with an insulated cover while the food and dish are onthe server. The server and the insulated cover may be cooperative forkeeping the food at a temperature above 140° F. for one hour (e.g., formore than one hour).

In accordance with one aspect of this disclosure, the body of the heatretentive server has an inner chamber, and the induction-heatable memberis positioned in the chamber. Thermal material is positioned in thechamber and envelopes (e.g., partially envelopes or fully envelopes) theinduction-heatable member. The thermal material is adapted for providingpredetermined conductive heat transfer from the induction-heatablemember to the body so that the temperature of at least a portion of thebody becomes greater than the heat deflection temperature of the body inresponse to the induction-heatable member being heated byelectromagnetic induction to greater than the heat deflectiontemperature of the body. More specifically, the induction-heatablemember may be heatable by electromagnetic induction to a firsttemperature that is greater than the heat deflection temperature of thebody, and the thermal material may be adapted so that at least a portionof the body is heated to a second temperature that is greater than theheat deflection temperature of the body in response to theinduction-heatable member being heated by electromagnetic induction tothe first temperature, wherein the second temperature is less than thefirst temperature. For example, the first temperature may be more than81° F. hotter than the second temperature.

The induction-heatable member may comprise a metal plate, or morespecifically a metal disk, and a porcelain enamel coating that partiallyor fully encloses the metal disk. The porcelain enamel coatingadvantageously seeks to cause uniform dissipation of heat from the metaldisk, and also serves as a protective coating, such as for inhibitingany rusting.

In one embodiment, the body of the server comprises an upper shell and alower shell, and the body's chamber is defined between the upper andlower shells. The thermal material that is positioned in the chamber andenvelopes (e.g., partially envelopes or fully envelopes) theinduction-heatable member may include insulation and buffering material.In one embodiment, the buffering material is positioned in the chamberbetween the induction-heatable member and the upper shell, and thebuffering material is adapted for providing predetermined conductiveheat transfer from the induction-heatable member to the upper shell sothat the temperature of at least a portion of the upper shell becomesgreater than the heat deflection temperature of the upper shell inresponse to the induction-heatable member being heated byelectromagnetic induction to a temperature greater than the heatdeflection temperature of the upper shell. More specifically, theinduction-heatable member may be heatable by electromagnetic inductionto a temperature (e.g., a relatively high temperature) that is greaterthan the heat deflection temperature of the upper shell, and thebuffering material may be adapted for providing predetermined conductiveheat transfer from the induction-heatable member to the upper shell sothat at least a portion of the upper shell is heated to a temperature(e.g., a relatively low temperature as compared to the relatively hightemperature of the induction-heatable member) that is greater than theheat deflection temperature of the upper shell.

In contrast, the insulation may be positioned in the chamber between theinduction-heatable member and the lower shell, and the insulation may beadapted for restricting conductive heat transfer from theinduction-heatable member to the lower shell so that the temperature ofthe lower shell does not exceed the heat deflection temperature of thelower shell in response to the induction-heatable member being heated byelectromagnetic induction to the temperature greater than the heatdeflection temperature of the upper shell. The heat deflectiontemperature of the upper shell may be substantially equal to the heatdeflection temperature of the lower shell.

The foregoing presents a simplified summary of some aspects of thisdisclosure in order to provide a basic understanding. The foregoing isnot an extensive summary and is not intended to identify key or criticalelements of the invention or to delineate the scope of the invention.The purpose of the foregoing summary is to present some concepts of thisdisclosure in a simplified form as a prelude to the more detaileddescription that is presented later. For example, other aspects of thisdisclosure will become apparent from the following.

BRIEF DESCRIPTION OF THE DRAWINGS

Having described some aspects of this disclosure in general terms,reference will now be made to the accompanying drawings, which are notnecessarily drawn to scale and may be partially schematic. The drawingsare exemplary only, and should not be construed as limiting theinvention.

FIG. 1 is a top perspective view of a heat retentive server, inaccordance with a first embodiment of this disclosure.

FIG. 2 is a cross-sectional view taken along line 2-2 of FIG. 1, whereinline 2-2 intersects and is perpendicular to a central axis of theserver, and wherein FIG. 2 is representative of all cross-sections takenalong lines that intersect and extend perpendicularly to the centralaxis of the server, in accordance with the first embodiment.

FIG. 3 is a partially exploded view showing the server exploded awayfrom an activator, and an insulated cover exploded away from the serverand a plate carried by the server, in accordance with the firstembodiment.

DETAILED DESCRIPTION

Exemplary embodiments of this disclosure are described below andillustrated in the accompanying figures, in which like numerals refer tolike parts throughout the several views. The embodiments describedprovide examples and should not be interpreted as limiting the scope ofthe invention.

Referring to FIGS. 1 and 2, a heat retentive server 10 of a firstembodiment of this disclosure is described in the following. The server10 includes an upwardly and outwardly extending polymeric ring 14mounted to a periphery of a central disk assembly 18, so that the servermay be characterized as being in the form of a round tray or plate-likestructure, although numerous other configurations are within the scopeof this disclosure, as will be discussed below. Referring also to FIG. 2and as discussed in greater detail below, at least one internal metallicplate, or more specifically a metallic disk 22, of the disk assembly 18may be heated by way of electromagnetic induction while the server 10 isupon an activator 5 containing one or more induction coils (not shown).Thereafter, or at any other suitable time, a dish, such as a plate 6,may be placed centrally upon the upper surface of the disk assembly 18so that the ring 14 extends around at least a lower portion of theplate. The dish, or more specifically the plate 6, may be made of chinaor other acceptable materials. The plate 6, as well as food 7 on theplate, may be covered with an insulated, dome-shaped cover 8 having alower periphery that substantially seals against an upper periphery ofthe ring 14. Typically the plate 6 and food 7 are covered with theinsulated cover 8 from shortly after the point in time at which theplate with food is placed upon the server 10 to shortly before the pointin time at which the food is to be consumed. Examples of covers, orlids, are disclosed in U.S. Pat. Nos. 4,982,722, 5,603,858 and6,670,589, and the disclosure of each of these patents is incorporatedherein by reference in its entirety. As an example of an advantage thatwill be discussed in greater detail below, the washed dish 6 may notneed to be preheated prior to placing the food 7 thereon, because theserver 10 may provide sufficient heat energy so that the food 7 may havea serving temperature of at least 140° F. after one hour irrespective ofwhether the dish is preheated or at room temperature when the food isplaced thereon.

Referring in greater detail to FIGS. 1 and 2, the disk assembly 18includes a body that is typically in the form of polymeric upper andlower shells 26, 28 that are fixedly connected to one another. Theshells 26, 28 may be connected in any suitable manner. For example, thering 14 is typically mounted to the periphery of the disk assembly 18 ina manner that at least partially holds (e.g., clasps) the shells 26, 28together, as will be discussed in greater detail below. In the firstembodiment, the upper and lower shells 26, 28 are also fixedly mountedto one another at annular inner and outer joints 32, 34, wherein theinner and outer joints 32, 34, like many other features of the server10, extend around and are coaxially arranged with respect to a centralaxis 38 of the server.

For each of the inner and outer joints 32, 34, the upper shell 26defines a downwardly oriented annular receptacle that is in snug receiptof an upwardly oriented annular protrusion of the lower shell 28. Priorto mounting the shells 26, 28 together, the downwardly oriented annularreceptacles of the upper shell 26 would be downwardly open, since theywould not yet be in respective receipt of the upwardly oriented annularprotrusions of the lower shell 28. Each of the downwardly orientedannular receptacles of the upper shell 26 is defined between a pair ofdownwardly extending, concentric portions of the upper shell.

For each of the inner and outer joints 32, 34, there may be an annularinterference fit between the annular receptacle of the upper shell 26and the annular protrusion of the lower shell 28. In addition and/oralternatively, for each of the inner and outer joints 32, 34, there maybe an annular connection (e.g., a sonic weld) between at least the tipof the annular protrusion and the apex of the annular receptacle of thejoint. For each of the inner and outer joints 32, 34, the positions ofthe annular receptacle and annular protrusion of the joint may bereversed. The upper and lower shells 26, 28 may be connected to oneanother in any other suitable manner.

The disk assembly 18 includes an outer chamber 42 that extends around aninner chamber 44 of the disk assembly. The chambers 42, 44 are definedbetween the upper and lower shells 26, 28, so that the inner chamber 44is circumscribed by the inner joint 32, the outer chamber 42circumscribes the inner joint, and the outer joint 34 circumscribes theouter chamber. The induction-heatable metallic disk 22 is positioned inthe outer chamber 42. The inner joint 32 extends through a central holein the metallic disk 22.

The metallic disc 22 is enveloped (e.g., partially enveloped or fullyenveloped) by thermal material that is within the outer chamber 42. Inthe first embodiment, the thermal material is layered, so that there arelayers 50, 52, 54 of thermal material (e.g., plies 50, 52 of insulatingmaterial and a ply of buffering material 54) that are in a stackedconfiguration, wherein each of the layers 50, 52, 54 is in the form of adisk with a central hole through which the inner joint 32 extends, andthe metallic disk 22 is positioned within the stack of layers 50, 52,54.

The layers 50, 52, 54 of thermal material are adapted for both retainingheat in the metallic disk 22, and directing heat from the metallic diskto the plate 6, or other object(s), that are upon the upper surface ofthe upper shell 26. More specifically and regarding the conductive flowof heat from the heated metallic disk 22 in an axial direction thatextends along and parallel to the central axis 38 of the server 10, therate of conductive heat flow (e.g., heat flux) through the upper layer54 of buffering material and the upper shell 26 exceeds the rate ofconductive heat flow (e.g., heat flux) through the lower andintermediate layers 50, 52 of insulation and the lower shell 28.

More specifically and in accordance with the first embodiment, outwardheat transfer through the lower shell 28 is not desired, and suchoutward heat transfer through the lower shell may be characterized asbeing heat loss to the system. Also, it is typically desirable for thelower shell 28 not to be hot to the touch so as not to cause a burninjury when the metallic disk 22 is hot. Accordingly, the lower andintermediate layers 50, 52 of insulation are adapted for substantiallyrestricting outward heat transfer through the lower shell 28.

In contrast, controlled, long-term, substantial outward heat transferthrough the upper shell 26 is desired. Accordingly, the layer 54 ofbuffering material serves as a buffer between the metallic disk 22 andthe upper shell 26. In the first embodiment, the layer 54 of bufferingmaterial fills the gap between the metallic disk 22 and the upper shell26, and the layer of buffering material is adapted for graduallytransferring heat from the metallic disk to the upper shell, wherein theheat transfer through the layer of buffering material is slow andgradual so that, while the metallic disk is sufficiently hot, thetemperature of the underside of the upper shell can exceed the heatdeflection temperature of the material from which the upper shell isconstructed, without damaging the upper shell.

In the first embodiment and as will be discussed in greater detailbelow, the disk assembly 18 may be configured (e.g., the layers 50, 52,54 are adapted) for providing predetermined conductive heat transferfrom the metallic disk 22 to the body (i.e., the upper and lower shells26, 28) of the disk assembly, so that, in response to the metallic diskbeing heated by electromagnetic induction to greater than the heatdeflection temperature of the body: the temperature of at least aportion of the body, namely at least a portion of the upper shell 26(e.g., the portion(s) of the upper shell that are in relatively closeproximity to the layer 54 of buffering material) become(s) greater thanthe heat deflection temperature of the body; and in contrast thetemperature of at least a portion of the body, namely the lower shell28, does not exceed the heat deflection temperature of the body. Otherconfigurations are also within the scope of this disclosure.

As mentioned above, the metallic disk 22 may be heated byelectromagnetic induction, and the disk assembly 18 is adapted so thatthere is predetermined conductive heat transfer from the heated metallicdisk, through the layers 50, 52, 54, and through the shells 26, 28. Inthis regard, the disk assembly 18 of the first embodiment includesdifferent features that are cooperative for providing the predeterminedconductive heat transfer, and the cooperative features generally includethe selection and arrangement of the layers 50, 52, 54, which will bediscussed in greater detail below, as well as provisions made in aneffort to exclude, or minimize, any water in the heat conductive pathsdefined by the disk assembly. For example, each of the lower andintermediate layers 50, 52 of insulation may be impregnated withsynthetic amorphous silica to produce a hydrophobic affect, as will bediscussed in greater detail below. In this regard, when the servers 10are used in conjunction with serving food 7, it is typical for theservers to be washed with soap and water, or the like, after each use;therefore, the servers may be repeatedly wetted and/or immersed inwater.

In accordance with the first embodiment, at least some of the adjacentstructures in the disk assembly 18 are in opposing face-to-face contactwith one another in a manner that inhibits any water from becomingintervened in at least some of the heat conductive paths that extend inthe axial direction of the disk assembly. More specifically, a broad,substantially planar, annular, lower face of the lower layer 50 ofinsulation is substantially parallel to and in opposing face-to-facecontact with a broad, substantially planar, annular, upper face of thelower shell 28. Similarly, a broad, substantially planar, annular, upperface of the upper layer 54 of buffering material is substantiallyparallel to and in opposing face-to-face contact with a broad,substantially planar, annular, lower face of the upper shell 26.

The metallic disk 22 is positioned between the lower and upper layers50, 54. More specifically, the metallic disk 22 is positioned betweenthe intermediate and upper and layers 52, 54. A broad, substantiallyplanar, annular, upper face of the intermediate layer 52 of insulationis substantially parallel to and in opposing face-to-face contact with abroad, substantially planar, annular, lower face of the metallic disk22. Similarly, a broad, substantially planar, annular, lower face of theupper layer 54 of buffering material is substantially parallel to and inopposing face-to-face contact with a broad, substantially planar,annular, upper face of the metallic disk 22. A broad, substantiallyplanar, annular, lower face of the intermediate layer 52 of insulationis substantially parallel to and in opposing face-to-face contact with abroad, substantially planar, annular, upper face of the lower layer 50of insulation. The stack, which includes the metallic disk 22 and thelayers 50, 52, 54, may be arranged differently. For example, the lowerand intermediate layers 50, 52 of insulation may be replaced with asingle layer of insulation, or any other suitable arrangement of theinsulation may be utilized.

In accordance with the first embodiment, the primary heat conductivepaths defined by the disk assembly 18 are associated with the outerchamber 42, since the metallic disk 22 is therein; therefore, the outerchamber is sealed in a manner that seeks to prevent water from enteringthe outer chamber. In this regard, the seal present at each of the innerand outer joints 32, 34 may be enhanced by and/or at least partiallyprovided by a gasket, or any other suitable sealing feature, in anysuitable configuration. More specifically, an intermediate O-ring 60 isadjacent the outer joint 34, and an annular washer 64 is adjacent theinner joint 32. As a more specific example, the intermediate O-ring 60is housed in an annular channel of the lower shell 28, and theintermediate O-ring is compressed between an annular lower wall of thelower shell's channel and an annular lower surface of the upper shell26. As another specific example, an annular inner portion of the washer64 is compressed between an annular, upwardly facing shoulder of thelower shell 28 and a downwardly oriented annular protrusion of the uppershell 26. Upper and lower surfaces of an annular outer portion of thewasher 64 are respectively in opposing face-to-face contact with anannular inner portion of the lower face of the metallic disk 22 and anannular inner portion of the upper face of the intermediate layer 52 ofinsulation.

As alluded to above, the inner portion of the ring 14 may becharacterized as being in the form of a permanently closed, annularclasp that is fixedly mounted onto the outer, annular, peripheral edgesof the shells 26, 28 in a manner that holds the shells tightly together.The ring 14 and/or the ring's clasping feature may be omitted, orprovided in any suitable manner. In the first embodiment, the ring 14includes an upper ring portion 70 and a lower ring portion 72, and thering's annular clasping feature is provided by fixedly joining togetherthe upper and lower ring portions 70, 72 so that outwardly extendingannular flanges of the shells 26, 28 are pinched between inwardlyextending annular flanges of the upper and lower ring portions 70, 72.

The upper and lower ring portions 70, 72 may be joined together in anysuitable manner, such as at an annular connection 78 between a lowerannular surface of the upper ring portion 70 and an upper annularsurface of the lower ring portion 72. The annular connection 78 betweenthe upper and lower ring portions 70, 72 may be formed in any suitablemanner. For example, the annular connection 78 between the upper andlower ring portions 70, 72 may be formed in a leakproof manner byplastic welding, fusing or heat sealing the respective annular surfacesof the upper and lower ring portions together. Suitable methods andapparatus for forming the annular connection 78 between the respectiveannular surfaces of the upper and lower ring portions 70, 72 may beavailable from Emabond Solutions of Norwood, N.J.

Seals between the outwardly extending annular flanges of the shells 26,28 and the inwardly extending annular flanges of the ring portions 70,72 may be enhanced by and/or at least partially provided by gaskets, orany other suitable sealing features, in any suitable configuration. Morespecifically, an upper O-ring 84 is positioned in an annular channeldefined in the outwardly extending annular flange of the upper shell 26,and the upper O-ring is compressed between an annular lower wall of theupper shell's channel and an annular lower surface of the inwardlyextending annular flange of the upper ring portion 70. Somewhatsimilarly, a lower O-ring 88 is positioned in an annular channel definedin the inwardly extending annular flange of the lower ring portion 72,and the lower O-ring is compressed between an annular lower wall of thelower ring portion's channel and an annular lower surface of theoutwardly extending annular flange of the lower shell 28.

Optionally, the lower shell 28 defines a central opening to the innerchamber 44, and a spring-loaded pressure relief valve 92 is mounted tothe lower shell for maintaining the central opening in a sealed closedconfiguration, except that the pressure relief valve is operative fortemporarily opening the central opening and thereby venting the innerchamber in response a predetermined differential pressure between theambient environment and the atmosphere in the inner chamber. Morespecifically, the opening to the inner chamber 44 may be at leastpartially defined by, or associated with, a valve seat, and a valve diskof the pressure relief valve 92 is typically urged and sealed againstthe valve seat by one or more springs. The valve disk may be temporarilypushed off of the valve seat, for venting the inner chamber 44, inresponse to any predetermined increase in pressure within the innerchamber, such as may occur in response to the metallic disk 22 beingsufficiently heated. An O-ring or any other suitable structure foraiding in the sealing may be mounted to and carried by the valve disk,so that the spring-driven valve disk forces the O-ring, or any othersuitable device, against the valve seat. Alternatively, any othersuitable type of pressure relieving device may be used, such as, but notlimited to, a “membrane” or diaphragm pressure relief valve. Examples ofpressure relieving devices are disclosed in U.S. Pat. No. 6,005,233, andthe disclosure of this patent is incorporated herein by reference in itsentirety.

For the purpose of providing a more specific example, a secondembodiment of this disclosure is described in the following, and thesecond embodiment is identical to the first embodiment, except for beingdescribed more specifically in the following; therefore, the samereference numerals are used. In accordance with the second embodiment:

-   -   the metallic disk 22 is a porcelain enamel coated metal disk,        and more specifically the metallic disk is a carbon metal disk        (the metal comprises carbon as an alloying element) with a        porcelain enamel coating;    -   each of the upper and lower shells 26, 28 is constructed of a        high temperature polymer material, more specifically each of the        upper and lower shells is constructed of reinforced polymer        material, and even more specifically each of the upper and lower        shells is constructed of a blend of modified polyphenylene ether        (PPE) and polyamide (PA) with 30% glass fill;    -   the lower layer 50 of insulation is 2 mm thick and impregnated        with synthetic amorphous silica so that it is hydrophobic, more        specifically the lower layer of insulation is a layer of silica        aerogel that is 2 mm thick, and more specifically the lower        layer of insulation is a 2 mm thick piece of silica aerogel        nanoporous insulation;    -   the intermediate layer 52 of insulation is 5 mm thick and        impregnated with synthetic amorphous silica so that it is        hydrophobic, more specifically the intermediate layer of        insulation is a layer of silica aerogel that is 5 mm thick, and        more specifically the intermediate layer of insulation is a 5 mm        thick piece of insulation formed of silica aerogel and        reinforced with a non-woven, glass-fiber batting;    -   the upper layer 54 of buffering material is a high temperature        silicone pad that is less than about 0.1 inches thick, more        specifically the upper layer of buffering material is a high        temperature silicone membrane that is 0.032 inches thick, and        more specifically the upper layer of buffering material is a        piece of high temperature Shore A silicone that is 0.032 inches        thick;    -   each of the O-rings 60, 84, 88 may be a nitrile O-ring, or an        O-ring constructed of any other suitable material;    -   the washer 64 is a high temperature silicone washer, more        specifically the washer is a high temperature silicone ring that        is flat and 0.064 inches thick, and more specifically the washer        is a flat piece of high temperature Shore A silicone that is        0.064 inches thick; and    -   each of the upper and lower ring portions 70, 72 of the ring 14        is Polypropylene.        Each of the dimensions specified above for the second embodiment        may be approximate, such that each of the dimensions specified        above for the second embodiment may be preceded by “about”.        Similarly, each of the dimensions specified above for the second        embodiment may vary within a reasonably suitable range/by a        reasonably suitable amount, which may be plus and/or minus 5%,        plus and/or minus 10%, plus and/or minus 15%, plus and/or minus        20%, or any other suitable amount.

Reiterating from above, the metallic disk 22 may be in the form of ametal plate, or more specifically a metal disk, that is coated withporcelain enamel, so that the porcelain enamel coating at leastpartially encloses, and typically fully encloses, the metal disk. Theporcelain enamel coating is schematically illustrated in FIG. 2 by therelatively thick line defining the periphery of the metallic disk 22.The porcelain enamel coating advantageously seeks to cause uniformdissipation of heat from the metallic disk 22, and also serves as aprotective coating, such as for inhibiting rusting of the metal disk.

Partially reiterating from above and in accordance with one specificexample of the second embodiment, each of the upper and lower shells 26,28 is constructed of polymer material (e.g., a blend of modifiedpolyphenylene ether (PPE) and polyamide (PA) with 30% glass fill) thathas a heat deflection temperature of 464° F. when tested with a load of264 psi. In use, the server 10 is typically not exposed to a load of 264psi. In a first example of operation of a specific version of the server10 of the second embodiment in which each of the upper and lower shells26, 28 is constructed of polymer material (e.g., a blend of modifiedpolyphenylene ether (PPE) and polyamide (PA) with 30% glass fill) havinga heat deflection temperature of 464° F. when tested with a load of 264psi, the porcelain enamel coated, carbon metal disk 22 reached a peaktemperature of 665° F. in response to being inductively heated by theactivator 5 (FIG. 3) for a period of twelve seconds, and the upper layerof buffering material 54 (in the form of pad of high temperature Shore Asilicone having a thickness of 0.032 inches) had a momentary peakoperating temperature of 600° F. in response to the heating of metaldisk 22.

In a second example of operation of the above-described specific versionof the server 10, the metal disk 22 reached a peak temperature of 630°F. at the end of being inductively heated by the activator 5 (FIG. 3);at a distance of 0.080 inches into the upper shell 26, the upper shellreached a maximum temperature of 492° F. (e.g., core temperature of theupper shell 26); and the buffering material 54 reached a temperature of570° F. That is, the metal disk 22 was heated by electromagneticinduction to a first temperature (e.g., 630° F.) that is greater thanthe heat deflection temperature of the body (e.g., the heat deflectiontemperature of the upper shell 26), and at least a portion of the body(e.g., at least a portion of the upper shell 26) was heated byconduction by way of the buffering material 54 to a second temperature(e.g., 492° F.) that is greater than the heat deflection temperature ofthe body (e.g., the heat deflection temperature of the upper shell 26).The second temperature (e.g., 492° F.) is less than the firsttemperature (e.g., 630° F.) by 138° F., or more generally by about 138°F. In the second example, the metal disk 22 was at a temperature of 160°F. at the beginning of the heating cycle, so that the second examplesimulates the server 10 being misused, since the metal disk maytypically be at ambient temperature at the beginning of a heating cycle.

In each of the first and second examples presented above, the values maybe considered to be approximate. The temperatures will vary because, forexample, the performance of the servers 10 may vary slightly from serverto server, and the performance of the activators 5 may vary slightlyfrom activator to activator.

In accordance with a more general example of the second embodiment, thebuffering material 54 is adapted for providing predetermined conductiveheat transfer from the metallic disk 22 to the upper shell 26 so thatthe temperature of at least a portion of the upper shell becomes greaterthan the heat deflection temperature of the upper shell in response tothe metal disk being heated by the activator 5/electromagnetic inductionto a temperature greater than the heat deflection temperature of theupper shell. As a more specific example, the heat deflection temperatureof the upper shell 26 may be about 464° F. when tested with a load of264 psi, the server 10 uniformly/as a whole may be at about ambient roomtemperature (e.g., about 75° F.) prior to being inductively heated bythe activator 5, the metal disk 22 may reach a peak temperature in arange of from about 580° F. to about 665° F. in response to beinginductively heated by the activator 5, and a portion of the upper shell26 may reach a peak temperature in a range of from about 460° F. toabout 525° F. in response to conductive heat flow (e.g., heat flux) fromthe metal disk 22, through the layer 54 of buffering material, to theupper shell 26. As a more general example, the heat deflectiontemperature of a portion of the upper shell 26 may be from about 417° F.to about 511° F., the server 10 uniformly/as a whole may be at aboutambient temperature (e.g., about 75° F.) to about 100° F. prior to beinginductively heated by the activator 5, the metal disk 22 may reach apeak temperature in a range of from about 522° F. to about 700° F. inresponse to being inductively heated by the activator 5, and a portionof the upper shell 26 may reach a peak temperature in a range of fromabout 414° F. to about 576° F. in response to conductive heat flow(e.g., heat flux) from the metal disk 22, through the layer 54 ofbuffering material, to the upper shell 26. When the server 10 isoperated as discussed above, the peak temperature of the upper shell 26,which is above the heat deflection temperature of the upper shell, maybe up to about 280° F. less than the peak temperature the metal disk 22;or the peak temperature of the upper shell 26, which is above the heatdeflection temperature of the upper shell, may be less than the peaktemperature the metal disk 22 in a range of from about 55° F. to about205° F., in a range of from about 108° F. to about 156° F., or a rangeof from about 120° F. to about 140° F. When the server 10 is operated asdiscussed above, the peak temperature of the metal disk 22 may be morethan 81° F., 108° F., 120° F., 140° F., 156° F. or 205° F. hotter thanthe peak temperature of the upper shell 26 and/or the peak temperatureof the metal disk 22 may be up to about 310° F. hotter than the peaktemperature of the upper shell 26.

In an exemplary method of using the server 10, the metal disk 22 isheated by the activator 5 to greater than the heat deflectiontemperature of the shells 26, 28, and then the dish 6 (FIG. 3), which isat about ambient room temperature (e.g., about 75° F.) is placed on theserver 10 as shown in FIG. 3. The food 7 (FIG. 3) may be placed on thedish 6 at any suitable time, such as prior to the dish being placed uponthe server 10. For example, the food 7 may weigh about twelve to fifteenounces, and may be at about 165° F. when it is placed on the dish. Thedish 6 with the food 7 thereon may be quickly placed upon the server 10,so that the dish is only slightly heated by the food prior to the dishbeing placed on the server. Accordingly, the dish 6 may be referred toas being at about ambient room temperature after the dish is slightlyheated by the food 7. The server 10 may provide sufficient heat energyto heat the dish and the food so that the food is above about 140° F.after an hour of sitting on the dish that is sitting upon the server 10.That is, in the exemplary method of this disclosure, the washed dish 6does not have to be preheated prior to placing the food 7 thereon,because the server 10 provides sufficient heat energy to provide thedesired result without preheating the dish, wherein the desired resultcomprises the food having a serving temperature of at least 140° F.after one hour. That is and in accordance with one aspect of thisdisclosure, the server 10 is constructed to control the direction andrate of heat transfer to facilitate the exemplary method of thisdisclosure. As mentioned above, typically the dish 6 and food 7 arecovered with the insulated cover 8 from shortly after the point in timeat which the dish with food is placed upon the server 10 to shortlybefore the point in time at which the food is to be consumed.Accordingly, the insulated cover 8 and the server 10 may be cooperativefor providing the above-discussed functionalities.

In contrast to the exemplary method of this disclosure, it isconventional for a dish that has been washed to thereafter be preheatedto at least 165° F. in a dish heater, and then for the food at atemperature of at 165° F. to be placed on the preheated dish prior toplacing the dish on an induction-based heat retentive server. It can bedisadvantageous to preheat numerous dishes, because doing so requiresspace and energy. Having to preheat numerous dishes may also be a safetyhazard, since foodservice operators may get burned by touching the dishheaters in certain spots.

In the exemplary method of this disclosure, any conventional dish heater(not shown) that is proximate the system of this disclosure may bebypassed (e.g., the dish 6 is not heated) between the washing of thedish 6 in a conventional manner and the placing of the dish upon theserver 10. Notwithstanding, this disclosure is not limited to requiringbypassing of any dish heater/the dish 6 may alternatively be heated by adish heater prior to placing the dish upon the server 10.

The activator 5 (e.g., its induction coil(s) and generator(s)) aretypically configured to be powerful enough to provide the valuesdiscussed above. For example, the activator 5 may include a guide orreceptacle for receiving the server 10, and the activator may provide apower output of 10 kilowatts for twelve seconds while the server isproperly positioned in the receptacle, so that the metallic disk 22 ofthe server is heated by way of electromagnetic induction. The activator5 may provide the power output in response to the server 10 initiallyengaging an activation switch. The activation switch may be positionedin the receptacle so that the activation switch is engaged by the server10 when the server is properly positioned in the receptacle. For coolingthe electronics within the activator 5, the rear wall of the activatormay be vented (e.g., louvered), and standoff structure(s) such asprojections, brackets or any other suitable spacers may project fromproximate the rear wall in a manner that seeks to prevent the vents inthe rear wall from becoming obstructed. Any other suitable activator 5may be used.

In the foregoing, examples are provided of features that are cooperativefor providing predetermined conductive heat transfer. However, it may bepossible to use a lesser number of the subject features and/or thesubject feature(s) in different configurations to provide thepredetermined conductive heat transfer, or the like; therefore, theprovision of specific examples herein is not intended to limit the scopeof this disclosure.

Whereas the disk assembly 18 and the ring 14 are often round in shape,they may be shaped differently, so that the server is oblong or in theshape of a quadrilateral, such as a parallelogram, or in any othersuitable shape. In addition, the obliqueness and/or height of the ring14 relative to the disk assembly 18 may vary, such as by the ring beingmore shallow and/or more upright, and the ring may be otherwise reducedin size or even omitted. As another example, one or more of the diskassemblies may be incorporated into a single tray.

The above examples are in no way intended to limit the scope of thepresent invention. It will be understood by those skilled in the artthat while the present disclosure has been discussed above withreference to exemplary embodiments, various additions, modifications andchanges can be made thereto without departing from the spirit and scopeof the invention as set forth in the claims.

What is claimed is:
 1. A heat retentive server comprising: a body havinga chamber, an upper shell, and a lower shell, the upper shell and thelower shell connected to one another, the chamber being defined betweenthe upper shell and the lower shell; an induction-heatable memberpositioned in the chamber; and a buffering material positioned betweenthe induction-heatable member and the upper shell, the bufferingmaterial configured to provide a predetermined conductive heat transferfrom the induction-heatable member to the body such that the server isconfigured to cooperate with an insulated cover covering a surface ofthe server with a dish and food placed upon the dish between theinsulated cover and the server to keep the food at a temperature above140° F. for one hour after the food and the dish are covered with thefood being at a temperature of about 165° F. when placed on the dish andthe dish being about room temperature when placed on the server, thebuffering material comprising: a lower insulating section positionedbetween the induction-heatable member and the lower shell; and an upperbuffering section positioned between the induction-heatable member andthe upper shell, the upper buffering section being less insulative thanthe lower insulating section.
 2. The heat retentive server according toclaim 1, wherein the induction-heatable member is heatable byelectromagnetic induction.
 3. The heat retentive server according toclaim 1, wherein the induction-heatable member comprises a metal plateand a porcelain enamel coating that encloses the metal plate.
 4. Theheat retentive server according to claim 1, wherein the bufferingmaterial comprises an inhibitively conductive hydrophobic material. 5.The heat retentive server according to claim 1, wherein the body isconstructed of a blend of polyphenylene ether (PPE) and polyamide (PA).6. The heat retentive server according to claim 1, wherein the bodyincludes a 30% glass fill.
 7. The heat retentive server according toclaim 1, wherein the buffering material is in opposing face-to-facecontact with both an upper surface of the induction-heatable member anda lower surface of the upper shell.
 8. The heat retentive serveraccording to claim 1, wherein the upper buffering section has athickness of less than about 0.1 inches.
 9. The heat retentive serveraccording to claim 1, wherein the upper buffering section is thinnerthan the lower insulating section.
 10. The heat retentive serveraccording to claim 1, wherein the upper buffering section or the lowerinsulating section comprises a silica aerogel.
 11. The heat retentiveserver according to claim 1, wherein the buffering material comprisesintermediate insulating section positioned between theinduction-heatable member and the lower insulating section.
 12. The heatretentive server according to claim 1, wherein the lower shell comprisesa pressure relieve valve configured to release pressure from the chamberwhen a predetermined differential pressure is reached between thechamber and the ambient environment.
 13. A heat retentive servercomprising: a body having a chamber, an upper shell, and a lower shell,the upper shell and the lower shell connected to one another, thechamber being defined between the upper shell and the lower shell; aninduction-heatable member positioned in the chamber; and a bufferingmaterial positioned between the induction-heatable member and the uppershell, the buffering material configured to provide a predeterminedconductive heat transfer from the induction-heatable member to the bodysuch that the server is configured to cooperate with an insulated covercovering a surface of the server with a dish and food placed upon thedish between the insulated cover and the server to keep the food at atemperature above 140° F. for one hour after the food and the dish arecovered with the food being at a temperature of about 165° F. whenplaced on the dish and the dish being about room temperature when placedon the server, wherein the buffering material comprises: a lower sectionbetween the induction-heatable member and the lower shell configured torestrict heat transfer through the lower shell; and an upper sectionpositioned between the induction-heatable member and the upper shell,the upper section configured gradually transfer heat from theinduction-heatable member to the upper shell.
 14. The heat retentiveserver according to claim 13, wherein the buffering material includes alower insulating material forming the lower section and an upperbuffering material forming the upper section.
 15. The heat retentiveserver according to claim 14, wherein the upper buffering material isdifferent from the lower insulating material.
 16. The heat retentiveserver according to claim 14, wherein the lower section includes anintermediate insulating material and a lower insulating material, theintermediate insulating material positioned between theinduction-heatable member and lower insulating material.
 17. The heatretentive server according to claim 13, wherein the induction-heatablemember comprises a metal plate and a porcelain enamel coating thatencloses the metal plate.
 18. The heat retentive server according toclaim 13, wherein the buffering material comprises an inhibitivelyconductive hydrophobic material.
 19. A heat retentive server systemcomprising: a heat retentive server according to claim 13; a dish; andan insulated cover for covering the dish and food while the dish is uponthe server and the food is upon the dish.
 20. A heat retentive serversystem comprising: a body having a chamber, an upper shell, and a lowershell, the upper shell and the lower shell connected to one another, thechamber being defined between the upper shell and the lower shell; aninduction-heatable member positioned in the chamber; a bufferingmaterial positioned between the induction-heatable member and the uppershell, the buffering material configured to provide a predeterminedconductive heat transfer from the induction-heatable member to the body,wherein the buffering material comprises: lower section positionedbetween the induction-heatable member and the lower shell; and uppersection positioned between the induction-heatable member and the uppershell; and an insulated cover configured to cover the dish with foodplaced upon the dish and the dish placed upon the server, the server andthe insulated cover configured to cooperate to keep the food at atemperature above 140° F. for one hour after the food and the dish onthe server are covered with the insulated cover, the food being at atemperature of about 165° F. when placed on the dish and the dish beingat about room temperature when placed on the server.